Technical data

Description of the individual
levels
The individual program processing levels and the corresponding user
interfaces are described in more detail in the following sections:
Section 4.4 describes the program processing levels
in RESTART.
Section 4.5 describes the program processing levels
in RUN
Sections 5.6 and 5.7 describe the error levels in RESTART
and RUN.
Example 2:
If an operation code error occurs in the LZF program processing level, the
system program attempts to call the BCF level (user interface OB 29). This
has, however, already been activated by the occurrence of a parameter error
(user interface OB 30) and has not yet been completely processed. Calling the
BCF level again at this point is not permitted; the CPU changes to STOP (see
Fig. 4-5).
if op code error
STOP
BCF
LZF
CYCLE
OB 27
OB 29
PB 5 FB 7
OB 30
OB 1
FB 2 FB 3
OB 31
FB 22
FB 21
error
if parameter
error
if substitution
Parameter error in FB 3:
OB 30 call /
BCF level
Runtime error processing OB 30:
OB 31 call /
LZF level
Op code error in FB 22
causes STOP
Fig. 4-5 Double call of error level BCD
Program Processing Levels
CPU 928B Programming Guide
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